The spinal column is a complex system of bones and connective tissues that provide support for the human body and protection for the spinal cord and nerves. The adult spine is comprised of an upper and lower portion. The upper portion contains 24 discrete bones, which are subdivided into three areas including 7 cervical vertebrae, 12 thoracic vertebrae and 5 lumbar vertebrae. The lower portion is comprised of the sacral and coccygeal bones. The cylindrical shaped bones, called vertebral bodies, progressively increase in size from the upper portion downwards to the lower portion.
An intervertebral disc along with two posterior facet joints cushion and dampen the various translational and rotational forces exerted upon the spinal column. The intervertebral disc is a spacer located between two vertebral bodies. The facets provide stability to the posterior portion of adjacent vertebrae. The spinal cord is housed in the canal of the vertebral bodies. It is protected posteriorly by the lamina. The lamina is a curved surface with three main protrusions. Two transverse processes extend laterally from the lamina, while the spinous process extends caudally and posteriorly. The vertebral bodies and lamina are connected by a bone bridge called the pedicle.
The spine is a flexible structure capable of a large range of motion. There are various disorders, diseases and types of injury which restrict the range of motion of the spine or interfere with important elements of the nervous system. The problems include, but are not limited to, scoliosis, kyphosis, excessive lordosis, spondylolisthesis, slipped or ruptured discs, degenerative disc disease, vertebral body fracture, and tumors. Persons suffering from any of the above conditions typically experience extreme or debilitating pain and often times diminished nerve function.
Spinal fixation apparatuses are widely employed in surgical processes for correcting spinal injuries and diseases. These apparatuses commonly employ longitudinally link rods secured to coupling elements, which in turn are secured to the bone by spinal bone fixation fasteners such as pedicle screws, hooks, and others. The opposing pair of longitudinally linked rods is commonly disposed along the long axis of the spine and is held in position relative to one another by cross-connector devices, also know as transverse connectors or transverse bridge elements. This hardware is placed perpendicular to the rods and provides torsional stability and rigidity.
To meet the problem of securely connecting two opposing spinal rods, a requirement exists to provide a transverse connector device that can easily be rotated about all three axes and translated along the longitudinal axis of the transverse connector during the course of the surgical procedure and then be securely locked into the desired position. In addition, the transverse connector should have the ability to secure to rods of various diameters and should be adaptable to fit around a multitude of pedicle screw heads. Also, the device should be configured to provide a low profile with the smoothest possible contoured surfaces to avoid irritation of adjacent soft tissue and thus promote healing and comfort for the patient post operatively.
Commonly, transverse connectors are connected to opposing rods midway between two pedicle screws in adjacent vertebrae increasing rigidity, but also adding stress to the construct. The devices illustrated in U.S. Pat. No. 6,736,817 issued to Troxell et al., U.S. Pat. No. 6,217,578 issued to Crozet et al., and U.S. Pat. No. 7,029,474 issued to Richelsoph et al. encompass this trait. Many devices have been invented for the purpose of stabilizing the spine to increase the rigidity of the structure. These devices have the ability to connect to the rod of their designated system, but cannot adapt to other spinal systems, a desirable feature in the case of re-operation or adding on to existing implanted hardware.
Therefore, a need exists for a transverse connector that is secured to a rod at the pedicle screw and can be adaptable to multiple size rods and pedicle screws on the market, while not interfering with the normal anatomy.